Having documentary-style video clips interspered amongst the entirety of the film really added to that charm, as did the relatively-lightning fast pacing of the second half for the main plot.
But of course, as charming as many of the aspects are, all infused with the signature passion and self-aware voice of Gainax (lots and lots of Trigger tropes that took the weeb world by storm in the 10s are very present here), it does feel middling at times due to the fact that it's trying to appeal to two extremely different audiences, necessarily, two opposite ends of a spectrum: anime noobies and anime vets.
But despite that stretched out feeling of duality, Otaku no Video still succeeds (and at times, utterly triumphs) solely due to that aforementioned Gainax passion.
It's a love letter to anime and to its boom during the 80s golden age. It takes all the facets of otaku culture, all of its obesessive tenets, its inherent patheticness, its disgusting flaws, and embraces them.
It doesn't praise them, nor dismiss them, but just says "this is part of who otaku are, and we are otaku."
Juxtaposed with that power fantasy plot of the main animation, and the entire film as a whole really just feels like a retrospective love letter, pinned on with musings of what could have been.
It might not work for everyone due to its split identity, but if nothing else, Otaku no Video is charming.
